Performance Tools
Render-Blocking Resources Checker
Check a page for render-blocking stylesheets and scripts in its <head> that could be slowing down first paint.
Enter a URL to check its <head> for render-blocking stylesheets and scripts that could be slowing down how fast your page first appears.
JustChecker tracks your website's performance continuously, catching regressions before your visitors notice.
Frequently Asked Questions
A CSS or JavaScript file loaded in a way that forces the browser to wait for it before it can display anything on screen - stylesheets without a restrictive media query, and scripts without async or defer, are the most common causes.
Add the async or defer attribute to your <script> tags - async loads the script in parallel and runs it as soon as it's ready, while defer runs it after the page has parsed, in order.
For CSS that's not needed immediately (like print styles), add a specific media attribute (e.g. media="print"). For critical CSS, consider inlining just what's needed for the initial view.